The present invention relates to a gas flushing or injection stone and a process for the manufacture thereof, particularly wherein a net is embedded in a refractory material or compound employed to form the stone, and such net subsequently is removed by burning or melting, with the result that a plurality of gas channels are formed in the stone.
Gas injection stones of this general type are disclosed in German DE 32 46 937 A1 and in German DE 35 03 221 C2. The flushing action or degree of gas injection is limited by the threads or webs of the net used to form the gas channels. If it is desired to increase the degree of gas injection, i.e. the gas permeability of the stone, the cross sections of the threads or webs of the net may be increased, such that the cross sections of the resultant gas channels are increased. This however results in a disadvantage in that the gas bubbles that flow into a molten material at an outlet end of the stone are undesirably large. Such large gas bubbles counteract the achieving of a gentle gas injection or flushing operation. Furthermore, a large cross section of the gas channels may lead to the penetration of the molten material into the outlet ends of the gas channels, and this is a highly undesirable result.
German DE-PS 38 02 657 discloses a gas flushing stone having a gas permeable spacing member that exhibits varying geometric shapes in the direction of wear of the stone. Thus, depending upon the state of wear of the stone at a particular time, a particular geometric pattern will become visible on the inner surface of the stone.